为了解决蒙特卡罗模拟S(α,β)模型只能求解特定温度条件下中子输运问题的局限性，建立了中子在不同温度液态水中输运的等效质量热运动模型。在分析自由气体热运动模型的基础上，采用不同的等效质量对中子与水中氢原子的弹性散射模拟过程进行改进，对中子穿过水层后的流量进行模拟计算，通过与S(α,β)模型的计算结果的比较，得到了5个不同的温度点水中氢原子的最佳等效质量。根据5个不同温度点的数据拟合给出了最佳等效质量和温度的函数关系。采用该模型计算得到的中子在不同温度条件下水中输运参数与S(α,β)模型相符。等效质量热运动模型突破了S(α,β)模型只能计算有限温度点的局限性，能有效处理300～800 K任意温度水中的中子输运问题。

In the Monte Carlo simulation, the S(α,β) model can only be used in some given temperature. The paper proposes the equivalent mass thermal motion model of neutron transport in water at different temperatures. The free gas thermal motion model is analyzed. Different equivalent masses are used to correct the neutron elastic scattering simulation of hydrogen in water, and the optimal equivalent mass of hydrogen in water at five different temperatures is given by comparing the result of the neutron flow through water layer with the S(α,β) model. According to the data of the five different temperature points, the formula of the optimal equivalent mass varying with temperature is fitted. The results of the equivalent mass thermal motion model are in accord with those of the S(α,β) model. The equivalent mass thermal motion model breaks the limitation of the S(α,β) model, and can deal with the neutron transport problems in water at arbitrary temperature between 300-800 K.